Many internal combustion engines for cars and vehicles use a throttle valve to control the amount of air entering the engine. The throttle valve may be opened to provide unimpeded air intake through a throttle body. Alternatively, the throttle valve may be closed to greatly restrict the passage of air. By controlling the amount of air the throttle valve forms part of the primary engine speed control. The throttle valve may be mechanically linked to an accelerator pedal to be opened or closed according to the pedal position of the accelerator.
Examples of conventional rotary throttle position sensors include Japanese Patent Kokai 7-151508.
In the following, a conventional rotary throttle position sensor is described referring to drawings. FIG. 9(a) illustrates a conventional rotary throttle position sensor as viewed from the bottom, with the cover removed to make the internal structure visible. FIG. 9(b) is a magnified view showing the key part of FIG. 9(a), rotor and retaining arm. FIG. 10 is a cross sectional view of the conventional rotary throttle position sensor. A cylindrical case 1 having a bottom comprises a retaining arm 2 extending from the inner wall surface towards the centre. A resistive film element 3 forms a resistive pattern(not shown) along the inner wall surface of case 1. A connector terminal 4 for connection with outside the case 1 is electrically coupled to the resistive film element 3. A rotor 5 is provided touching the retaining arm 2 and comprises, at the end of a support block 9, a brush 6 which slides on the resistive pattern of resistive film element 3. The case 1 comprises a pair of retaining arms 2 each having an indentation 8 for engagement with a protrusion 7 provided at the outer periphery of the rotor 5.
The conventional rotary throttle position sensor is assembled during the manufacture with the protrusion 7 engaged with the indentation 8 provided in the retaining arm 2, for setting the brush 6 at a desired initial position.
The above described structure, however, has drawbacks in that, although during manufacture the brush 6 may be aligned to a specified position by inserting the protrusion 7 on the periphery of rotor 5 in the indentation 8 of the retaining arm 2 the manufacturing work while making sure whether the engagement of protrusion 7 with indentation 8 is surely kept or not may be a fairly complicated operation. Furthermore, in a case when the protrusion 7 is erroneously inserted during the manufacture to the indentation 8 the rotor 5 may be positioned eccentric to case 1 already at "as manufactured" stage. If such a rotary throttle position sensor is mounted on a throttle shaft to be sensed, the rotor 5 would be broken or the sensor would not be installed at a desired place of the throttle body.
The present invention addresses the above described drawbacks and aims to present a rotary throttle position sensor that has an improved reliability .